Various types of devices are utilized as temperature sensors to measure the temperature of different environments. In high temperature areas or “hot zones”, operation of such devices is problematic. One portion of the temperature sensor, such as a thermistor, must be placed in the hot zone to detect the temperature, and even in the hot zone there may be large and frequent temperature variations. Measurement or control circuitry and lead wires must be placed outside of the hot zone—i.e., in a low temperature zone—to prevent damage. Nonetheless, there must be some portion of the sensor which traverses both zones to maintain an electrical connection between the thermistor and the associated circuitry.
Those skilled in the art have attempted to provide relief from excessive stress and strain caused by the high temperatures and sizeable operating temperature ranges. One known technique matches as closely as possible the temperature coefficient of the materials used in all portions of the temperature sensor. Another known technique includes extra material or wire to account for stresses and strains resulting from large temperature fluctuations. Such efforts result in a more costly temperature sensor, however, and/or a temperature sensor which still may degrade and become unreliable after a relatively short period of time, due to the effects of high temperature and frequent temperature excursions. In but one example, automobile exhaust temperature sensors are placed in an operating area or hot zone which reach temperatures as hot as 1000° C., as used in diesel filter trap regeneration applications. Large temperature excursions from 1000° C. or higher, to as low as the surrounding ambient temperature, can occur several times a day. Other attempts to solve the problem, such as the use of thermocouple sensors, have also been found to be costly and less than satisfactory overall.